Conventionally, in an internal combustion engine provided with both a variable compression ratio mechanism capable of changing the top dead center position of the piston and a variable valve train mechanism capable of changing the operational characteristics of an intake valve and/or exhaust valve, such as described in Japanese Patent Application Publication No. 2005-2931 A, it is necessary to secure the shortest distance (clearance) of closest approach of the valve and the piston approach relatively large in view of the varieties of movements of these parts so that the valve and piston would not interfere with each other with any chance.